Slurry catalyst compositions and means for their preparation are known in the refining arts. Some examples are discussed below.
U.S. Pat. No. 4,710,486 discloses a process for the preparation of a dispersed Group VIB metal sulfide hydrocarbon oil hydroprocessing catalyst. Process steps include reacting aqueous ammonia and a Group VIB metal compound, such as molybdenum oxide or tungsten oxide, to form a water soluble oxygen-containing compound such as ammonium molybdate or tungstate.
U.S. Pat. No. 4,970,190 discloses a process for the preparation of a dispersed Group VIB metal sulfide catalyst for use in hydrocarbon oil hydroprocessing. This catalyst is promoted with a Group VIII metal. Process steps include dissolving a Group VIB metal compound, such as molybdenum oxide or tungsten oxide, with ammonia to form a water soluble compound such as aqueous ammonium molybdate or ammonium tungstate.
U.S. Pat. Nos. 5,164,075 and 5,484,755 (the latter patent being incorporated by reference) disclose processes for preparation of high activity slurry catalysts for hydroprocessing heavy hydrocarbon oils produced from Group VIB metal compounds. An aqueous mixture of the metal compound is sulfided with from greater than about 8 to about 14 standard cubic feet of hydrogen sulfide per pound of Group VIB metal. These patents demonstrate a process of forming a slurry catalyst precursor and adding it to a heavy feed oil to form the active catalyst. These patents do not, however, demonstrate the criticality of the oil viscosity in the formation of a highly active catalyst composition, nor the significance of maintaining water in the liquid phase in a crucial reaction step.
In the inventions disclosed in U.S. Pat. Nos. 5,164,075 and 5,484,755, the failure to form the oil and water emulsion or the slurry phase results in an inactive catalyst or a catalyst having low activity.
U.S. Pat. Nos. 5,162,282 and 5,178,749 are directed to processes for hydroprocessing of heavy hydrocarbonaceous oils. In U.S. Pat. No. 5,162,282, a catalyst precursor is prepared by reacting a Group VIB metal compound with a sulfiding agent in an aqueous environment, substantially in the absence of oil. The precursor is heated to convert it to an active catalyst, which subsequently contacts feed at hydroprocessing conditions. In U.S. Pat. No. 5,178,749, an active catalyst slurry is prepared by sulfiding an aqueous mixture of a Group VIB metal compound with hydrogen sulfide gas. The slurry is introduced, along with the oil to be treated, into a fixed or ebullating bed of hydrodesulfurization-hydrodemetalation catalyst at hydroprocessing conditions. Although both of these patents disclose hydroprocessing with catalyst formed from precursors or slurries comprising Group VIB metal compounds, neither involves the use of oils in the formation of the catalyst precursors or slurries.
This application discloses a new slurry catalyst composition that is highly active. This activity results from preparation of the catalyst using a process employing a single hydrocarbon oil (preferably a vacuum gas oil) having an appropriate viscosity range at 212° F. Product yields are primarily in the middle distillate range.